3GPP that is a standardization group of the third generation mobile communication system is studying a communication scheme that becomes an evolved version of W-CDMA, HSDPA and HSUPA, that is, 3GPP is studying Evolved UTRA and UTRAN (Another name: Long Term Evolution or Super 3G, to be referred to as E-UTRA hereinafter) (refer to non-patent document 1, for example).
Different from W-CDMA and the like, E-UTRA realizes all packet access including radio sections. Especially, in the uplink, although the component of the packet access is introduced in HSUPA which is an evolved version of W-CDMA, HSUPA uses circuit switching type communication based on dedicated channels. Uplink access schemes are largely different between E-UTRA and earlier W-CDMA or HSUPA.
As main features, E-UTRA adopts all packet access, and adopts time/frequency packet scheduling. Thus, in each cell, mobile stations to which uplink radio resources are assigned are different for each TTI (Transmission Time Interval) and for each resource block (RB). As a result, the other-cell interference amount applied to neighboring cells due to uplink transmission in a cell largely varies every TTI and largely varies every RB.
FIG. 1 shows an example of variation of the interference amount for each TTI. In FIG. 1, the horizontal axis indicates TTI, and the vertical axis indicates normalized interference power, and FIG. 1 shows Round Robin (RR) scheduling and Proportional Fairness (PF) scheduling. As a result, in both of the scheduling schemes, the uplink SINR (Signal-to-Interference plus Noise Power Ratio) largely varies, so that communication quality deteriorates. Therefore, how the variation of other-cell interference should be decreased is an issue.
As a method for decreasing the other-cell interference, a method using a control signal called Overload Indicator (OLI) is adopted in HSUPA and E-UTRA (refer to non-patent document 2, for example). As shown in FIG. 2, each base station measures the uplink interference amount, and reports the interference amount to neighboring cells via a network using OLI. The base station receiving OLI from a neighboring cell causes a mobile station to decrease transmission power when it is determined that the interference amount exerted on the neighboring cell is large. Accordingly, the other-cell interference amount can be controlled, that is, can be decreased, for example, so that throughput characteristics of the whole system and user throughput characteristics can be improved.    [Non-patent document 1] 3GPP TR25.814 (V7.1.0), “Physical Layer Aspects for Evolved UTRA”, September 2006.    [Non-patent document 2] 3GPP, TS 25.309, (V6.6.0), “FDD Enhanced Uplink Overall Description Stage 2,” March 2006.